Electro phonometer and phonoscope



-I. H. FARNHAM.

ELECTED PHONOMETER AND PHONOSGOPE.

(No Model.)

Inventor:

Patented July 14,1891.

' 1 W nease UNITED STATES PATENT OFFICE.

ISAIAH H. FARNHAM, OF VELLESLEY, ASSIGNOR TO THE NEYV ENGLAND TELEPHONE AND TELEGRAPH COMPANY, OF BOSTON, MASSACHUSETTS.

ELlECTRO PHONOMETER AND PHONOSCOPE.

SPECIFICATION forming part of Letters Patent No. 455,815, dated July 14, 1891. Application filed February 13, 1891. Serial No. 381,365. (No model.)

To all whom it may concern;

Be it known "that I, ISAIAH H. FARNHAM, residing at \Vellesley, in the county of Norfolk and State of Massachusetts, have invented certain Improvements in Electro Phonom eters and Phonoscopes, of which the following is a specification.

This invention is as electro phonometer and phonoscope.

It is well known that the lines of electric circuits extended between different stations are, in addition to their legitimate workingcurrent, traversed by many foreign and intrusive currents of electricity, usually in a state of perpetual variation of strength and often also of direction. Regardless of the character of the invaded electric circuit, these intrusive currents tend to interference with the legitimate current and to distort, retard, or disturb the signals produced thereby. The operative currents ordinarily circulating in telephone-circuits are of minute volume, and for this reason the receiving-telephone requires to be and is an instrument extremely sensitive to electric changes. This being the case, it is evident that in telephone-lines the interfering ten dency of the intrusive currents may be expected to manifest itself to a pronounced extent, resultingin noises in the telephone, which vary in degree of intensity from a gentle murmur to a sound which overpowers all others, and which also has a great variety of character. This expectation is fully realized in practice. The interfering currents are due to a great number of causes. They are induced by virtue of the proximity of arc lighting circuits, alternating currents, lncandescent lighting circuits, electric railways, and harmonic telegraph circuits. They sometimes occur by conduction or absolute transfer of current from the above agencies and many others unnecessary to mention. Inasmuch as all of the interfering currents are the enemies of and oppose the proper use of the lines, it becomes necessary to cultivate their acquaintance and to study theircharacter and differences, and to determine their comparative values for the purposes of bringing them under control, of suppressing them, if possible, and in any event to diminish their a part of this specification, Figure l is a perspective view of one form of instrument embodying my invention which has been found convenient in practice. Fig. 2 is a longitudinal sectional elevation thereof. Fig. 3 is a plan view. 4 is a' cross-section on line a: roof Fig. 2, and Fig. 5 is a detail. Fig. 6 is a modification.

The essential features of the instrumentare respectively a magnet, adiaphragm mounted in front thereof in close proximity thereto, a suitable coil or helix of insulated wire adapted by suitable connections for inclusion in any electric circuit, and capable of being moved or slid along the magnet from one end to the other, suitable means for efiecting the said movement, an index or scale properly graduated, and a pointer attached to the movable coil and denoting the advance thereo on the said graduated scale.

As shown in Fig. 1,the inclosing case, which may be made of hard wood, hard rubber, or

other similar material, has two sides 4 and 8,

and is provided with a base a, to which it is secured; Its ends are respectively closed by end pieces 3 and 1, the latterbeing centrally perforated, and fitted by means, such as a small rigid tube 15, (see Fig.2,) whereby a flexible tube h, terminated bya convenient ear-piece, maybe attached. Bindin -screws 9 and 10, constituting the instrument-terminals, are affixed to the rear end piece The 9 top piece 5 is slotted from end to end,and on one side of'its outer surface is a graduated scale '7, which may be integral therewith or separate and secured in any desired manner. A lever g projects from the interior through IOC the slot 6, terminated by afinger piece or button f, andprovided with the pointerj, which is associated with the scale.

In Fig. 1 I have shown the tube has being twisted round the instrument, so as to present a compact appearance when not in use.

The scale 7 is shown asbeing so graduated that each division represen s five units; but it can of course be divided to a much finer degree of graduation, if clesired' In Fig. 3 the longer division-marks, each denoting twenty units, are correspondingly designated.

Between the end piece 1 and the end of the casing is a frame-piece 2, forming a seat for the diaphragm D, which-is clamped between its front surface and the end plate 1, the said endplate being slightly excavated or otherwise. conformed to form a flat vocalizingchamber. A circular space is cut through the center of the said frame-piece 2, and Within the said frame and crossing its central space from the upper to the lower sides is mounted a bar I), which in turn is centrally perforated for the admission of the active pole of a magnet m, extending from one end of the case to the other, which pole, passing through the said' bar, is adjusted in close proximity to. the diaphragm D; The magnet can be secured in place by the screws, passing throughthe back end piece, or in any preferred manner.

An electro-magnetic helix 0 of insulated wire, similar in size and construction to those used in the ordinary hand-telephone, is secured'to ablock d, of non-conducting material, such as hard rubber, audits ends terminate in. binding-screws13 and 14, mounted thereon, and from thence are continued by flexible conductors 11 and 12 (which may, if preferred, be included in a single cord) to the instrument-terminals 9 and 10.

The construction and arrangement of the coil, its supporting-back and moving lever,

and its relation to the magnet are more clearly shown in the detail drawing, Fig. 5. The lever 9 being secured to the blockd, both coil. and supporting-block are centrally perforated,.and are capable of beingslid or moved onthe magnet m with. great facility, the crossbar forming the front limit and the end piece 3 the back limit of their traverse. Since the bearing-surface upon the magnet is produced by a hole passing through both coil and block, itissufficiently long to prevent any opposition to the movement of the coil attributable to lateral play and consequent friction. By means of the handle f the coil can be moved as desired, an d'it may be prevented from moving tooeasily by causing the lever to press elastically against one edge of'the traverse slot or byproviding an extra springfor that purpose. Other modes of moving the said coil along the magnet maybe'adopted. For example, I may provide a threaded hole through the block d, forming a nut for a screw of suitable pitch and construction, the said screw to be operated' by a screw-head at the rear end of the casing. This modification is indicated in Fig. 6.

In the operation of my instrument it is connected with any desired circuit and the coil brought up to its front limit. The observer listens at the ear-piece and notes the amount of disturbance. He then slides the coil backward and finds that the'disturbing sound decreases in a regular manner, the reason, of course, being that-the coil through which the intrusive currents are circulating as it is moved away from the magnet-pole has a continually-decreasing influence over the magnetism of said pole, which magnetism is therefore maintained more constant, resulting in a more steady attraction of the dia-' phragm, the vibrations of which, therefore, are diminished. directly as the distance the coil is moved, and resulting also'in a consequent and proportionate decreaseof therdisturbing sounds. WVhen the coil isslid back so far that the sounds are normal, there being substantially no disturbance, the. position of the index-finger upon the scale is observed and the indication represents the comparative intensity of the disturbance in arbitrary units. By forming a record of these observations I am enabled to compare oneline with another, the disturbance on one date with that of the same line on another date,.or of a given line at differenttimes of' the same day, so as to divide up the amountsof disturbances due to difierent causes.- By my instrument the difference in the severity of disturbance caused by electric railway. arc lighting; and alternating incandescent lighting systems can be observed'and recorded. It is also-usefnl in determining the amount of benefit. derived from the use of a return-conductor or other attempts for the suppression of inductive disturbance, in comparing the merits of one transmitter with another, and in determining the talking qualities of ditferentilines and lines having different lengths of cable and underground conductor.

Having now fully described. my'invention and its .mode of operation, I claime-- 1. The hereinbefore-described method of comparing disturbing currents in electric circuits, which consists in causing them-to vary the field of a magnet-pole exercising attraction uponv avibratory diaphragm, in noting the sounds produced by thesaid' diaphragm under said variation, and then in Withdrawing the said. currents gradually from said pole until the said sounds cease, andlnoting the extent of separation, substantially as-described.

2. The electro-phonometer described herein, comprising a magnet, a vibratory diaphragm in close proximity to the polethereof, an electro-magnetic coil or helixadapted: for inclusion inan electric circuit mounted on said magnet and adapted to vary the magnetism of its pole, means, as indicated, for moving or sliding the said coil on the said magnet,

whereby its inductive influence thereon may be varied,and a scale and pointer, the latter being attached to said coil and adapted to move over the former and to indicate thereon the extent of movement of said coil.

3. In an electro phonometer or phonoscope, a magnet, a vibratory diaphragm mounted in close proximity to the pole thereof, and a coil or helix of insulated wire adapted for inclusion in an electric circuit mounted on said magnet and capable of being slid or moved thereon from its active pole rearwardly, and vice Versa, in combination with an actuating device for moving said coil, and a pointer and scale-indicator, whereby the extent of said motion may be determined.

4. In an instrument for observing and comparatively measuring electrical disturbances in telephone-circuits, a magnet, a vibratory diaphragm mounted in close proximity to the pole of said magnet, a coil or helix of insulal'ed wire and connections for including the same in circuits to be tested, the said coil being loosely mounted on said magnet and adapted to be slid from one end to the other and to vary the magnetism of the active pole thereof in differing degree according to its position, and a lever for moving the said coil on the said magnet, secured at one end to said coil and provided with a handle at the other, substantially as described.

5. The combination, in an instrument for measuring disturbances on telephone-lines, of a vibratory diaphragm, a bar-magnet having one pole in close proximity to and exercising attraction on said diaphragm, and a movable magnetism -varying coil adapted to be included in the circuit to be tested, mounted loosely on said magnet and capable of being slid thereon between its active and inactive poles, the disturbing sounds emitted by the diaphragm being at amaxi mum when the said coil immediately surrounds the active pole and decreasing as the said coil is slid away therefrom in the direction of the other pole.

G. In an electro phonometer or phonoscope, the combination of an inclosing case, a diaphragm mounted at one end thereof, an earpiece therefor, a bar-magnet inclosed in said case and having one pole in close proximity to said diaphragm, a movable coil of insulated Wire mountedon said magnet and capable of sliding thereon from the active pole rearwardly, and vice versa, a limit-stop for said coil determining its forward position, a 1ongitudinally-slotted cover for said case, a graduated scale mounted thereon, a lever secured inwardly to said movable coil, projecting through the slot in said cover, and provided at its outer end with a handle or finger-piece to move the said coil, and an index-finger car ried by said lever, moving therewith over said scale, and indicating thereon the comparative values of disturbing currents, all substantially as described, and for the purposes specified. Y

7. The combination, in an instrument for comparatively measuring disturbances due to intrusive currents on telephone-lines, of a telephone-diaphragm, ear-piece orear-tube, and magnet, with a movable coil orhelix of insulated wire and connections to place the same in a circuit to be tested, the said coil normally surrounding the active pole of the magnet to produce the maximum manifestation of disturbance, but being capable of sliding rearwardly on said magnet to a point of minimum disturbance, a graduated scale, and a needle or point moving with said coil and indicating on the scale the extent of motion and thereby the degree of disturbance.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 5th day of February, 1891.

ISAIAH H. FARNHAM.

lVitnesses:

GEO. WILLIS PIERCE, J OSEPH A. GATELY. 

